Rotary kiln for chemical and metallurgical processes



E y w E n 0 VMM N no@ 1 7 y 5 W l, w w W W w. 7 7 m M w a w 7 0 Q u w E N. an 5, S s N 2 w u Z y m uw@ s WF mn.. 3 o A@ m M m H n. IIHUIII m E 1 w N A A o Y .I s m\ m m m. Q M K. w w wh w W W ,WIN

ROTARY KILN FOR CHEMICAL AND May 9, 1950 Filed Jan. 17, 1948 May 9, 1950 w. K. sPRouLE ET AL 2,507,123

ROTARY KILN FOR CHEMICAL AND METALLURGICAL PROCESSES Filed Jan. 17, 1948 3 Sheets-Sheet 2 ipa/PME/vr INVENTORS May 9, 1950 w. K. SPROULE ET AL. 2,507,123

ROTARY RIEN ROR CHEMICAL ANO METALLURCICAL PROCESSES Filed Jan. 17, 1948 3 sheets-sheet s ATTORNEY Patented May 9, 1950 ROTARY KILN FOR CHEMICAL AND METALLURGICAL PROCESSES William Aeelvin Spronlc and Charles .Edward Young, 'Copper Cliff, and Roy Lincoln Snitch. Coniston, ntario, Canada, as signors to The International Nickel Company, Inc., New York, N. Y., a corporation of leaware Application January 17, 1948, Serial No. 2,838 In Venezuela January 31, 1947 The present invention relates in general to apparatus for treatment of ores at elevated temperatures and, more particularly, to rotary kilns designed to effect controlled high temperature reduction preparatory to the recovery of nickel from limonitic, silicate and roasted sulphide ores by the ammonia leaching process, and to effect controlledcooling` of the heated ores before discharge.

Rotary kilns have long been proposed for the reduction of nickel ores prior to recovery of nickel by the ammonia leaching process. It has been found, however, that the usual types of rotary kiln do not yield satisfactory results, particularly when coal or oil-fired.

The improved rotary kiln embodying the present invention meets the conditions necessary for satisfactory reduction for commercial recovery of nickel by the ammonia leaching process, particularly from lateritc ores containing nickel and cobalt in small amounts, for example, Vores of the types found in Venezuela, New Caledonia, the Celebes and Cuba. Such ores contain less than about 5% nickel, variable amounts of iron, silica, magnesia, and combined water of hydrationjand are commonly high in free moisture.

The present invention contemplates an improved rotary kiln designed for use with the ammonia leaching process for the recovery of nickel. The ammonia leaching process includes the steps of controlled heating and reducing the ores at elevated temperatures and cooling under controlled conditions. If desired, the reduction can be followed by oxidation and re-reduction at lower temperatures to further improve in economical manner the recovery of nickel from the ores by ammoniacal leaching. A preferred process for utilizing the novel rotary kiln disclosed in the present application is described in the co-pending Queneau, Borland and Renzoni application, Serial No. 778,558, now Patent No. 2,478,942.

In obtaining high nickel recovery in accorde ance with the present invention, the general procedure first involves the steps of drying the ore and, if the particle size of the ore is too coarse for optimum nickel recovery, then comminuting the ore. If desired, exhaust gases from the reduction kiln can be used for drying. The finely divided oreis then fed to the improved rotary kiln which embodies novel features of construction and arrangements of structural elements contributing to the substantial improvement and eniciency attained by the process while avoiding the objectionable and detrimental con- 6 Claims. (C1. 23--279) dltions such as have been experienced .in theuse of prior art types of rotary reduction kilns. Y'

It is on .object of, the present invention to prof vide a rotary kiln which, particularly in treating lowfsrade nickel-@Outillrlin,g laterlto ores, will result .in an output of material wherein@v high. proportion of the nickel isn a form solublefin ammoniacal leachingsolution.

A further objeotof .the improvements contrib: utlpeto the new .results .is to provide a novel. kiln structure-whereby detrimental effeotaref sulting from contact between incompletely re acted `fuel-air mixtures and the ore, are avoided.

Still .another object of the invention is to provide a kim wherein oontaots between the ore and harmfully high temperature ,zones in the flame are avoided.

It is another object. of the invention to provide a structure effective in maintaining a positive pressure of gas in the kiln s0 as to obtain the im: portant advantage of. eliminating undesirable air leaks into the kiln or parts thereof, and also to minimize objectionable,stratification of gases of different Composition in the .dehydration and reduction Azones o f the kiln..

Other objects and advantages of the invention Will become apparent v,from the following descripf non taken .in .conjunction with the accompanying drawings, in which:

' Fie. l is a .vertical longitudinal sootioxl oto rotary kiln embodying the present invention;

Fie. 2 depicts .a detailed verticalV longitudinal section of the .ore-receiving yen d o f the novel rotary kiln illustratedin Fig. V1;

Fig. 3 is a detailed vertical longitudinal secon-ion of the ore-dischargeendof the novel kiln illus,- trated in Fig. 1;

Fig. 4 isthe end .elevation lof the ,orefdischarge end of the kiln witha portion broken away to show the spiral ore-lifters; and

Fig. 5 is a section elevation at location .5-5 of the kiln shown in Fig. 1.

Referring more particularly to Fis. l. the drawing illustrates a rotary tube-type furnace .or kiln embodying the present mention.. The :novel kiln has a steel .cylinder or shell l which is lined with y,an insulating, heatfresisting lining ,2, yThe kiln is rsupported by rolls 3, bearing on Iriding rines 4 and can be .rotated .either .by rolls 3 if they are powered byrotatng drive Shaft 01' by a `*201iventional. bullgear 5, Longitudinal positioning of the kiln .can be accomplished by rolls `t .bearing laterally `on, riding; Alfngs ,4, .Gases fromthe yfeed end .of the kiln` discharge into otake .'l and then, if Y required, into conventional dust collecting equipment. Flow of these gases is controlled by an adjustable damper 8 (Figs. 1 and 2) which is maintained in sliding contact with the gas discharge end ofthe kilnand through which screw conveyor-t and supplementary airv pipe I extend. This damper is an important feature of the invention and is preferably adjusted to maintain a positive gas pressure, for vexample, about 0.05 to about 0.25 inch of water within the kiln to provide a method of excluding air therefrom.

Fig. 2 illustrates in detailfapreferred example of the ore-receiving end of the kiln. At the oredischarge end of the kiln-',-whe're therotating shell joins the stationary en`d housing, shown in Fig. 1 and Fig. 3, gas seals are provided. Use of conventional draft-control dampers -in conventional type nues leading from the kiln were found to be unsatisfactory for pressure control. In addition to eliminating undesirable air leaks into theV kiln andvinto the lreduced-ore cooler, the novel damper 8, in conjunction with gas seals at the ore-discharge end, minimizes stratification of gases of different compositions in the dehydrating and reduction zones. When such means are not employed, such as is the case with conventional kilns, relatively cool gases, sometimes containing oxygen, flow from the gas discharge housing into the kiln and along the floor of the kiln as far as the reduction zone, with damaging eiect on the reduction of the ore. Chains can be used as means to improve heat transfer between gases and ore near the ore-charging end, where use of lifters might result in high dust loss. Sensible heat in the reduced ore can be recovered by use of the heated cooling water, for instance, from spray cooling water or from pan 20, for boiler feed, or by air cooling under induced draft and use of the thus-heated air for fuel combustion purposes;- Means provided for temperature control include a multiple point recording pyrometer with thermocouples extending through the Ikiln wall and connected with copper rings Il encircling the kiln which are engaged by 'suitab1e brushes connected to the pyrometer. Gas is sampled at various'points along the` kiln andthe gases are analyzed automatically for combustiblesc'ontent. Oxygen in the cooling zone Z-3 or" in'the subsequent re-reduction and cooling zones ofthe oxidation-reduction solubility control apparatus, if such is used, is analyzed by means of an instrument sensitive to as little as 0.005% oxygen. As a further feature for obtaining a more effective exposure of ore to the reducing gasesI in the heating and reduction zones, provision can be made to impart a degree of"stirring or lifting or cascading of the ore through the gas by the employment of lifters 26, shown in Figs. 1 and 5, protruding inwardly, for example, about 3 inchesjto 9 inches from the inner periphery ofthe kiln; These ore lifters can be made of either brick or heat-resisting alloy s teel members designed ink correlation with the rotational speed of the kiln and thedegree of stirring required.

. lIn general, the length of the kiln,considered with relation to its diameter, rate of ore feed, time necessary to obtain the desired degree of reduction and other variables, is such as to establish, at the elevated,orereceiving end of the chamber, a drying and heating zone Z-I communicating with a succeeding reduction zone Z-2 which, in turn, communicates with the finalv cooling zone Z-3 at ,the delivery end of the kiln, all three zones being integral. When subsequent oxidation and re-reduction of the reduced ore is practiced, for instance, according to the process disclosed in the co-pending Queneau, Borland and Renzon application, Serial No. 778,558, the oxidation step may be conducted in the end or cooling zone Z-3 in the kiln, after which the ore is re-reduced and finally cooled in a separate apparatus.

In the operation of the kiln, flow of ore is countercurrent to the flow of the reducing combustion gases resulting from combustion of fuel introduced at the ore-discharge end of the furnace through fuel burner I2 mounted on Watercooled support I3 (Fig. 3). Products from the burner pass into a combustion chamber I4. This combustion chamber or muiiie is encircled or surrounded by an extension of the shell I in a manner providing a cooling zone or jacket Z-3 for the reduced ore in its passage to an ore discharge port I5. Ignition of the fuel takes place in the usual small ignition muflie or tile I6 integral with chamber I4, after which the ignited fuel and air or oxygen-enriched air enter the novel combustion chamber I4. The combustion chamber is formed of a cylinder of insulating and refractory material supported either within the discharge end of shell I or within an eXtension of shell I, preferably by means'of perforated spacing rings or spacers I'I. The entry ports in ring I8 between the reducing zone Z-2 and the cooling zone Z-3, and the perforations in spacing rings II are of suiiicient size to permit entry of the ore to the annular cooling chamber, passage therethrough and thence to the outgoing ore-discharge port I5. The aforementioned ports in ring I8 are, however, sufficiently smallthat migration of combustion gases into the cooling chamber can, if desired, be prevented by introduction of a. controlled atmosphere into said cooling chamber through gas inlet I9 (Fig. 3). Cooling action at the discharge end of the kiln is provided by water bath 20 or by other suitable means. The annular` cooling chambei` between the shell and the combustion chamber opens only at the ore-discharge end into discharge port I5, and, at its forward end, only into the reducing zone of the kiln through openings in ring I8, whereby the cooling occurs entirely within a controlled atmosphere.

Other integral or separate coolers, of known designs and permitting cooling of the ore under controlled atmosphere, may be employed in place of the type of cooler described above. Where it is desired to discharge the ore at elevated tem perature, for example, into an oxidation-reduction apparatus according to the process disclosed in the co-pending Queneau, Borland and Renzoni application, Serial No. 778,558, the water spray or Water bath 20 is not employed and the outer shell surrounding the combustion chamber is lined with refractory insulating material in order to prevent excessive cooling of the ore before discharge into said oxidation-reduction apparatus. I

The ore discharge end of the kiln is sealed by discharge housing 2i maintained in sliding contact with the kiln at seal rings 22 and 22A (Fig. 3) by means of tension springs (Fig. 1) or by other suitable means. The discharge housing 2| is supported by pivoted members 35 (Fig. 1). Ore is lifted from the annular space between the combustion chamber I4 and the outer shell I by means of spiral lifter blades 24 located between the burner end of the combustion chamber and the kiln end plate 25 (Fig. 3). Spiral ore-lifters 24 lift the ore and discharge it through port I5,

from' where it fallsV through seal: 21 through; al

discharge chutel 28 to screw conveyor; 29 leading.;

tmeitherv a. quench tank or.- to other units of equip..- ment for subsequent treatment, such as in the., aforementioned` oxidation-reduction apparatus. Minor quantities of gas and dust which may. leak. pastrseal'rings Eland 22A are removed by suction. on a hood -Sil (Fig. 3). Passage of gas or ore dust between the discharge housing 2| and the flameV issuing'f'romthe burner is prevented by extension 3i of thefkiln which makes sliding contact. with thedischarge housing between seal rings 32 and:

32A-A (Fig. 3). Stationary seal ring 32A .makes a slid-ingt with the stationary discharge housing andfis held in contact with moving ,seal ring 32 by pressure from resilient packing material 36.

which inturn is heldin place by adjustable angle ring 31. The packing material it? also functions toprevent' gas escape between seal ring 32A andV the sleeve of the discharge housing'. Limited ilexibilityis thus provided between stationary seal rings 22A and 32A order that gas-tight sealsl can be maintained by pressure betweenseals 22 and-22A- and between seals 32 and 32A. A cleanout` and explosion safety door 34 and a discharge chute clean-out port 38 are provided at the discharge-end of the kiln.

The nely divided ore for treatment in the novel kilnr can be introduced into the kiln by a variety of means. Thus, the ore can be transferred fromme-charging bin B, through an oremixing conveyor equipped with a reagent-chargingport R to screw conveyor 9 and then to zone Z-| in the kiln, such as shown in Fig. l and, in more detail, in Fig. 2. In the present apparatus, thedelivery end of screw conveyor 9 is in close proximity to the inner periphery of thekiln in order'that the delivery of the ore thereto be substantiallybeneath the bed of ore under treatment, thereby reducing dust losses.

The ore introduced in this manner is iirst heated and dehydrated in the dehydrating and heating-zone Z-i and then is treated within the reducing zone Z-2. Good results are obtainable in thisv kiln when employing pulverized solid fuel, commercial grades of light or heavy fuel oils, or gas. The novel combustion chamber i4, by virtue of size and shape, provides sufficient ame retention time to permit fuel, introduced through the burner l2, to be thoroughly combusted, to the extentY permitted by the proportion of oxygen used, before contact with the ore is made. In thisy manner, the novel design of combustion chamber-is of great value in minimizing contamination of the reduced ore with the products of partialcombustion, such as certain hydrocarbons, which are detrimental to the obtaining of best resultsA in the subsequent extraction of nickel. Contact. between the reduced ore and uncombined oxygen from the burner air or oxygen is also minimized. Furthermore, overheating of the .ore by comparatively high temperature zones inthe ame near the burner is avoided. The contour of the inner surface of the novel com-Y bustion chamber, combined with its rotating movement, serves to minimize detrimental accumulation of ore particles within the combustionchamber. Combustion of fuel in an external chamber and use of the resulting combustion gases inthe kiln involve both the establishment of a separate operation and the inevitable occurrence of heat losses, both of which are avoidedv by the unitary construction of the present novel kiln. Stationary refractory ignition tile, some. times usedin conjunction-with oiland gas burners, are toolsmall to;accomplishnsatisfactorilyrtlisv desired result. combustion chamber will, of course, varywiththe; size of. the,V kiln andv to someextentwth the typo:v

of fuel employed; A; combustion chamber about;` 5 feet long andE of thev proportions il1ustratedif in Fig; 1 hasbeen fo,und,satisiactory for a; kiln;-

about 50 feetzlong and-'aboutfeetginsidediameter. In. general, for best results, commerciali sized kilns. require combustion chambers having an internal volume preferably larger than aboutv 50,:cubicifeet. The improved large rotating. come.

bustion chamber or muiile I4 permits mainte.4

nance within the kiln of a reducing atmosphere containing,A upto'. aboutx30.% by.volume of car--A bon monoxide plus hydrogen, anda ratio ofv car..`

bon monoxide plus hydrogen to carbon. dioxide.`

plus water vapor of more than 2te l, when using-Y commercial grades of oil fuel. and non-preheatedzf air. Thisresult is accomplished withminimum contamination. of theore by excess combustion.

productsI and without interferingV with the heats.4 ing of the ore to the desired temperatures. Regus, lation of Oreretention time is accomplished; by controlling the feed rate, kiln slope and rotation. rate, and by-,use of retaining dams or diagonal: blacling. Kiln sections-of enlarged diameter may.y be used: to control retention time ofthe ore with.` in the`r kiln. Use of oxygenated-or preheated air:- tOsupport uel combustioniin the novel combus.- tionv chamber permits-.use of stilly more strongly,- reducingigases, permits-increased nickel recovery and/or permits increased feed rates of the ore. through the kiln, and'decreases dustl losses. Ther1 kiln can be providedawith means-for introducing supplementary air or oxygen for combustion purposes inlthe dehydrating and heatingy zoneaZf-.L Such means areknownto those skilled, in the art, and can, for instance, be piper lll,- which extends along the kiln a distance usually betweenonefourth and one-half thelength of the kiln and? which permits rapidy heating ofthe orel to thc--v desired reducing temperature range without use, ofk excessiveamounts of fuel.. TheV air or (iXi/gen. is supplied topipe lil by,;means of rotating-joint- 33 (Fig. 2.)'. The` controlled additionof-supplies. mentary air or oxygen also serves to regulatethe; ratel of heating within the range commonly prac. ticed in thel reduction of ores. However, such regulation of` heating ratev is, metallurgical-ly; speaking, less important than provision ofadequate chemical reactionl timel in the temperature.;z range of aboutv l200 F. togaboutilQOi F. When treating ore low in iron, forexample, certain ores., such as those foundI inA Venezuela, it has been; discovered .that immersingfgthe;reducediand cooled; ore from the kiln into thelleaching solution per mits at least %-nickel recovery. from-ores containingfless than'2-.0% nickel. However; thekilp product can-if desired, bertreatedinsteadfat lo.w.-. er temperatures by asolubilitycontrol operation; first by partial oxidation and then by reareduc. tion` of the treated ore prior to immersion in leaching solution, such as` by the process de-y scribedin the co-pending Queneau, Borland and; Renzoni application, Serial No. 778,558.

As illustrated in Fig. 1, the'sections of the kiln defining the dehydrating and. heating zone and the reducing zone are lined' with insulating brick. 2, hay-ing a specicgravitygof less than abouti-.0. Previously, kilns for ore treatment at elevatedl temperatureabove 1400" F: have been linedlwith iirebrick (apparent specific gravity about: 2.0.1701r 2.5') or.` other.l relatively heavy. briok'withoutfhigh.

i insulating. qualities;v Sometimes.v azlayer.; offinsus.,

The dimensions of. the novlf lating refractory is placed between this inner lining and the steel shell. We have now discovered that particularly when treating lateritic, nickel-containing ores, a better kiln performance as regards heat loss and lining life can be obtained by use of an insulating lining alone, constructed, for example, of porous reclay brick or castable insulating refractory having an apparent specific gravity of about 0.50 to 1.25. In this manner, the crushing action of a relatively heavy inner lining on an insulating lining is avoided. In addition. the kiln shell, supports and drive may be of lighter, less expensive construction when omitting the heavy refractory lining previously thought necessary in kilns for use at temperatures above about 1200 F. The wellknown deformation of circular kiln cross sections under the action of gravity tends to disintegrate refractory linings. The much lighter construction of the present novel kiln decreases any such deformation and, in combination with angle stiffeners on the kiln shell and the annular bearing rings 4, serves to minimize lining disintegration.

Although the present invention has been described in conjunction with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such variations and modifications as, for instance, the use of the present novel kiln in the treatment of roasted iron sulde ore containing nickel with or without copper, are to be considered within the purview of the specication and the scope of the appended claims.

We claim:

1. An improved rotary kiln for chemically and metallurgically treating ore comprising a rotatable kiln shell having an ore-charging port at one end, an annular ore-discharging port at the other end, a light-weight, insulating lining of specific gravity between about 0.5 and about 1.25, ore-litters extending longitudinally along the inner surface of the shell; rolls in external contact with said shell for positioning, supporting and rotating said shell on a central longitudinal axis inclined downwardly toward the annular, oredischarging end of Said shell; a stationary gasdischarge off-take containing a, damper maintained in sliding contact with the ore-charging port of said rotatable shell to obtain positive gas pressures between about 0.05 and about 0.25 inch of water in said shell whereby air infiltration and gas stratification are substantially reduced within the kiln; an ore-charging, screw conveyor extending through said gas-discharge off-take, said damper and said ore-charging port into said shell to discharge ore downwardly into said shell near the ore-charging port and in proximity to the lower segment of the inner periphery of said shell; an annular cooling chamber integral with and substantially co-axially aligned with said shell, said annular chamber having an ore-entry port at one end common to the annular ore-discharging port of said shell and having an oredischarging port provided with spiral, ore-lifting blades; external water sprays for cooling said annular cooling chamber; a combustion chamber integral with and substantially co-axially aligned internally with said shell and said annular cooling chamber by spacers constructed to permit passage of ore through said annular cooling chamber, said combustion chamber opening at one end into said shell at the annular ore-discharging port end thereof, having a burner port atthe other end and having an internal volume sunicient to permit complete reaction of all gases contained therein before the reaction products of said gases are discharged into the kiln shell; a, stationary ore-discharge housing maintained in sliding, substantially gas-tight contact with said annular cooling chamber to cooperate with said damper in maintaining positive gas pressures and in reducing to a negligible degree air infiltration and gas stratification within the kiln, said oredischarge housing having a burner substantially co-axially aligned with and directed into the burner port of said combustion chamber, having a port for introducing controlled atmospheres into said annular cooling chamber, and having a substantially gas tight, ore discharge chute opening into the ore-discharging port of said annular cooling chamber whereby ore can be treated on a commercial scale in the improved rotary kiln under continuously controlled conditions of temperature and atmosphere to obtain an industrial product having desired chemical and metallurgical characteristics.

2. An improved rotary kiln for chemically and metallurgically treating ore comprising a rotatable kiln shell having an ore-charging port at one end, an annular ore-discharging port at the other end, a light-weight, insulating lining of specific gravity between about 0.5 and about 1.25, ore-lifters extending longitudinally along the inner surface of the shell; a stationary gasdischarge ofi-take containing a damper maintained in sliding Contact with the ore-charging port of said rotatable shell to obtain positive gas pressures in said shell whereby air iniiltration and gas stratification are substantially reduced within the kiln; an ore-charging, screw conveyor extending through said gas-discharge olf-take, said damper and said ore-charging port into said shell to discharge ore downwardly into said shell near the ore-charging port and in proximity to the lower segment of the inner periphery of said shell; an annular cooling chamber integral with and substantially co-axially aligned with said shell, said annular chamber having an ore-entry port at one end common to the annular ore-discharging port of said shell and having an oredischarging port provided with spiral, ore-lifting blades; a combustion chamber integral with and substantially co-axially aligned internally with said shell and said annular cooling chamber by spacers constructed to permit passage of ore through said annular cooling chamber, said combustion chamber opening at one end into said shell at the annular ore-discharging port end thereof, having a burner port at the other end and having an internal volume sufficient to permit complete reaction of all gases contained therein before the reaction products of said gases are discharged into the kiln shell; a stationary ore-discharge housing maintained in sliding, substantially gas-tight contact with said annular cooling chamber to cooperate with said damper in maintaining positive gas pressures and in reducing to a negligible degree air inltration and gas stratification within the kiln, said ore-discharge housing having a burner substantially co-axially aligned with and directed into the burner port of said combustion chamber, having a port for introducing controlled atmospheres' into said annular cooling chamber, and having a substantially gas-tight, ore-discharge chute opening into the ore-discharging port of said annular cooling chamber whereby ore can be treated on a commercial scale in the improved rotary kiln tionary gas-discharge off-take containing ai damper maintained in: sliding contact withl the ore-charging port of said rotatable shell to obtain positive gas pressures in said shell whereby air' inltration and gas stratification are substantially reduced within'the kiln; an ore-charger extending through. said gas-discharge off-take, said damper and said ore-charging port; an annular cooling chamber` integral with and substantially co-axially aligned with said shell, said annular chamber having an ore-entry port at one end common to the annular ore-discharging port of said shell and having an ore-discharging port; a combustion chamber integral with and substantially co-aXially aligned internally with said shell. andA said annular cooling chamber by spac-l ers constructed to permit passage of ore through said annular cooling chamber, said combustion chamber opening at one end into said shell at the annular ore-discharging port end thereof, having a burner port at the other end and having an internal volume sufficient to permit complete reaction of all gases contained therein before the reaction products of said gases are discharged into the kiln shell; a stationary ore-discharge housing maintained in sliding, substantially gas-tight contact with said annular cooling chamber to cooperate with said damper in maintaining positive gas pressures and in reducing to a negligible degree air inltration and gas stratification Within the kiln, said ore-discharge housing having a burner substantially co-axially aligned With and directed into the burner port of said combustion chamber, having a port for introducing controlled atmospheres into said annular cooling chamber, and having a substantially gas-tight, ore-discharge chute opening into the ore-discharging port of said annular cooling chamber whereby ore can be treated on a commercial scale in the improved rotary kiln under continuously controlled conditions of temperature and atmosphere to obtain an industrial product having desired chemical and metallurgical characteristics.

4. An improving rotary kiln for chemically and metallurgically treating ore comprising a rotatable kiln shell having an ore-charging port at one end, an annular ore-discharging port at the other end, a light-Weight, insulating lining of specic gravity between about 0.5 and about 1.25; a damper maintained in sliding Contact with the ore-charging port of said rotatable shell to obtain positive gas pressures in said shell whereby air infiltration and gas stratication are substantially reduced within the kiln; an ore-charger extending through said damper and said orecharging port; an annular cooling chamber integral with and substantially co-axially aligned with said shell, said annular chamber having an ore-entry port at one end common to the annular ore-discharging port of said shell and having an ore-discharging port; a combustion chamber integral with and substantially co-axially aligned internally with said shell and said annular cooling chamber by spacers constructed to permit passage of ore through said annular cooling chamber, said combustion chamber openingfat one-end' into said shell at the annular ore-discharging port end thereof, having a burner port at the other endV and having an internal volume sufficient to permit complete reaction of all gases contained therein before thev reaction products of said: gases are discharged into the kiln shell; a'stationary ore-discharge'housing maintained in sliding, substantially gas-tight* contact with said vannular cooling chamber to cooperate with said damper i-n maintaining'positive gas pressures and in reducing .to a negligible degree air infiltration and'gas stratification within-the kiln, said oredischa-rgehousing having a burner substantially "co-axially aligned--withf-and directed into Vthe burner port offsaidcombustion chamber, having a-v port for introducing. controlled atmospheres into' said annularv cooling chamber, and having asubstantially gas-tight, ore-discharge chute openinginto thev ore-'discharging port of said annular cooling chamber wherebyrore can be treated on a commercial scale in the improved rotary kiln under continuously" controlled conditionsof temperature andY atmosphere to obtain anindustrial product havingY desired chemical'a-nd metallurgical characteristics.

5. An improvedirotary kiln for chemically and metallurgically treating .ore comprising av rotatable lined kiln shell having an ore-charging port at one end, an annular ore-discharging port at the other end; a damper maintained in sliding contact with the ore-charging port of said rotatable shell to obtain positive gas pressures in said shell whereby air inltration and gas stratication are substantially reduced within the kiln; an ore-charger extending through said damper and said ore-charging port; an annular cooling chamber integral With and substantially co-axially aligned with said shell, said annular chamber having an ore-entry port at one end common to the annular ore-discharging port of said shell and having an ore-discharging port; a combustion chamber integral with and substantially coaxially aligned internally with said shell and said annular cooling chamber by spacers constructed to permit passage of ore through said annular cooling chamber, said combustion chamber opening at one end into said shell at the annular oredischarging port end thereof, having a burner .port at the other end and having an internal volume sufficient to permit complete reaction of all gases contained therein before the reaction products of said gases are discharged into the kiln shell; a stationary ore-discharge housing maintained in sliding, substantially gas-tight contact with said annular cooling chamber to cooperate with said damper in maintaining positive gas pressures and in reducing to a negligible degree air infiltration and gas stratication within the kiln, said ore-discharge housing having a burner substantially co-axially aligned with and directed into the burner port of said combustion chamber, having a port for introducing controlled atmospheres into said annular cooling chamber, and having a substantially gas-tight, ore-discharge chute opening into the ore-discharging port of said annular cooling chamber whereby ore can be treated on a commercial scale in the improved rotary kiln under continuously controlled conditions of temperature and atmosphere to obtain an industrial product having desired chemical and metallurgical characteristics.

6. An improved rotary kiln for chemically and metallurgically treating ore comp-rising a rotatable lined kiln shell having an ore-charging port at one end, an annular ore-discharging port at the other end; a damper maintained in sliding contactv with the ore-charging port of said rotatable shell to obtain positive gas pressures in said shell whereby air infiltration and gas stratification are substantially reduced with the kiln; yan ore-charger extending through said damper and said ore-charging port; an annular cooling chamber integral with and substantially co-aXially aligned with said shell, said annular chamber having an ore-entry port at one end common to Yto the annular ore-discharging port of said shell and having an ore-discharging port; a combus- Vtion chamber integral with and substantially coaxially aligned internallyfwithsaid shell and said said annular cooling chamber by spacers constructe'd-.to permit passage of ore through said annular cooling chamber, said'combustion chamber opening at one end into said shell at the annular"oredischarging port-fend thereof, having a. burner 'port at the other end and having an internal volumev suicient to permit complete re action of all gases contained therein before the reaction products of said'ga'ses are discharged linto the kiln shell; a stationary ore-discharge housing maintained in sliding, substantially gastight contact with said annular cooling chamber to cooperate with said damper in maintaining positive gas pressures and in reducing to a negligible degree air inltration and gas stratication within the kiln, said ore-discharge housing having a burner substantially co-axially aligned with and directed into the burner port of said combustion chamber, and having a substantially gastight, ore-discharge chute opening into the oredischalging port of said annular cooling chamber whereby ore can be treated on a commercial scale in the improved rotary kiln under continuously controlled conditions of temperature and atmosphere to obtain an industrial product having desired chemical and metallurgical characteristics.

WILLIAM KELVIN SPROULE. CHARLES EDWARD YOUNG. ROY LINCOLN SNITCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,000,267 Jackson Aug. 8, 1911 1,171,583 Benson Feb. l5, 1916 1,510,149 Fasting Sept. 30, 1924 1,754,854 Gelstharp Apr, 15, 1930 2,173,182 Ronne Sept. 19, 1939 Certicate of Correction Patent No. 2,507 ,123 May 9, 1950 WILLIAM KELVIN SPROULE ET AL.

It is hereby certiiecl that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 11, line 6, for the Word With read within;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the oase in the Patent Oflice.

Signed and sealed this 15th day of August, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. AN IMPROVED ROTARY KILN FOR CHEMICALLY AND METALLURGICALLY TREATING ORE COMPRISING A ROTATABLE KILN SHELL HAVING AN ORE-CHARGING PORT AT ONE END, AN ANNULAR ORE-DISCHARGING PORT AT THE OTHER END, A LIGHT-WEIGHT, INSULATING LINING OF SPECIFIC GRAVITY BETWEEN ABOUT 0.5 AND ABOUT 1.25, ORE-LIFTERS EXTENDING LONGITUDINALLY ALONG THE INNER SURFACE OF THE SHELL; ROLLS IN EXTERNAL CONTACT WITH SAID SHELL FOR POSITIONING, SUPPORTING AND ROTATING SAID SHELL ON A CENTRAL LONGITUDINAL AXIS INCLINED DOWNWARDLY TOWARD THE ANNULAR, OREDISCHARGING END OF SAID SHELL; A STATIONARY GAS-0 DISCHARGE OFF-TAKE CONTAINING A DAMPER MAINTAINED IN SLIDING CONTACT WITH THE ORE-CHARGING PORT OF SAID ROTATABLE SHELL TO OBTAIN POSITIVE GAS PRESSURES BETWEEN ABOUT 0.05 AND ABOUT 0.25 INCH OF WATER IN SAID SHELL WHEREBY AIR INFILTRATION AND GAS STRATIFICATION ARE SUBSTANTIALLY REDUCED WITHIN THE KILN; AN ORE-CHARGING, SCREW CONVEYOR EXTENDING THROUGH SAID GAS-DISCHARGE OFF-TAKE, SAID DAMPER AND SAID ORE-CHARGING PORT INTO SAID SHELL TO DISCHARGE ORE DOWNWARDLY INTO SAID SHELL NEAR THE ORE-CHARGING PORT AND IN PROXIMITY TO THE LOWER SEGMENT OF THE INNER PERIPHERY OF SAID SHELL; AN ANNULAR COOLING CHAMBER INTEGRAL WITH AND SUBSTANTIALLY CO-AXIALLY ALIGNED WITH SAID SHELL, SAID ANNULAR CHAMBER HAVING AN ORE-ENTGRY PORT AT ONE END COMMON TO THE ANNULAR ORE-ENTRY CHARGING PORT OF SAID SHELL AND HAVING AN OREDISCHARGING PORT PROVIDED WITH SPIRAL, ORE-LIFTING BLADES; EXTERNAL WATER SPRAYS FOR COOLING SAID ANNULAR COOLING CHAMBER; A COMBUSTION CHAMBER INTEGRAL WITH AND SUBSTANTIALLY CO-AXIALLY ALIGNED INTERNALLY WITH SAID SHELL AND SAID ANNULAR COOLING CHAMBER BY SPACERS CONSTRUCTED TO PERMIT PASSAGE OF ORE THROUGH SAID ANNULAR COOLING CHAMBER, SAID COMBUSTION CHAMBER OPENING AT ONE END INTO SAID SHELL AT THE ANNULAR ORE-DISCHARGING PORT END THEREOF, HAVING A BURNER PORT AT THE OTHER END AND HAVING AN INTERNAL VOLUME SUFFICIENT TO PERMIT COMPLETE REACTION OF ALL GASES CONTAINED THEREIN BEFORE THE REACTION PRODUCTS OF SAID GASES ARE DISCHARGED INTO THE KILN SHELL; A STATIONARY ORE-DISCHARGE HOUSING MAINTAINED IN SLIDING, SUBSTANTIALLY GAS-TIGHT CONTACT WITH SAID ANNULAR COOLING CHAMBER TO COOPERATE WITH SAID DAMPER IN MAINTAINING POSITIVE GAS PRESSURES AND IN REDUCING TO A NEGLIGIBLE DEGREE AIR INFILTRATION AND GAS STRATIFICATION WITHIN THE KILN, SAID OREDISCHARGE HOUSING HAVING A BURNER SUBSTANTIALLY CO-AXIALLY ALIGNED WITH AND DIRECTED INTO THE BURNER PORT OF SAID COMBUSTION CHAMBER, HAVING A PORT FOR INTRODUCING CONTROLLED ATMOSPHERES INTO SAID ANNULAR COOLING CHAMBER, AND HAVING A SUBSTANTIALLY GAS - TIGHT, ORE - DISCHARGE CHUTE OPENING INTO THE ORE-DISCHARGING PORT OF SAID ANNULAR COOLING CHAMBER WHEREBY ORE CAN BE TREATED ON A COMMERCIAL SCALE IN THE IMPROVED ROTARY KILN UNDER CONTINUOUSLY CONTROLLED CONDITIONS OF TEMPERATURE AND ATMOSPHERE TO OBTAIN AN INDUSTRIAL PRODUCT HAVING DESIRED CHEMICAL AND METALLURGICAL CHARACTERISTICS. 